Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$22.97	12.622%	$25.8693	$25.87	$25.85	$25.90
Purchase #2	$33.45	3.597%	$34.6532	$34.65	$34.65	$34.70
Purchase #3	$150.83	9.505%	$165.1664	$165.17	$165.15	$165.20
Purchase #4	$186.75	13.794%	$212.5103	$212.51	$212.50	$212.50
Purchase #5	$134.47	7.505%	$144.562	$144.56	$144.55	$144.60
Purchase #6	$148.61	10.437%	$164.1204	$164.12	$164.10	$164.10
Purchase #7	$249.32	8.579%	$270.7092	$270.71	$270.70	$270.70
7 purchase totals =	$926.40		$1,017.5908	$1,017.59	$1,017.50	$1,017.70